One of conventional apparatuses for controlling the shift between two and four-wheel drivings is described in Japanese Patent laid open No. 61-119425 (119425/1986). The apparatus for controlling the shift between two and four-wheel drivings comprises a first sensor for detecting a shift member of a transfer means to be shifted, and a second sensor for detecting a revolution velocity of a propeller shaft wherein a shift member of an axle shaft is shifted when the second sensor detects the revolution velocity of the propeller shaft to be increased up to a transient building-up level whereby the shift is finished from two to four-wheel drivings.
In the conventional apparatus for controlling the shift between two and four-wheel drivings, however, the shift is not performed from two to four-wheel drivings as smoothly as expected because the shift member of the axle shaft is delayed to be actuated, for instance, by 0.07 to 0.1 sec. so that the difference of revolution velocities is occured between the propeller and axle shafts for the reason why such a delaying time can not be actually avoided in actuating any mechanical means.